U.S. Pat. Nos. 3,959,974 and 4,301,655, issued to Thomas, disclose internal combustion engines whose power is increased and efficiency improved by cyclically injecting water through the cylinder head into the combustion space above the piston, in the case of U.S. Pat. No. 3,959,974; and by injecting water into a steam generating cavity formed in the cylinder head in the case of U.S. Pat. No. 4,301,655.
While both patented structures achieve their stated objectives, both possess some drawbacks in terms of manufacturing costs and operational efficiency, and, accordingly, the object of this invention is to improve on the two prior patented arrangements and the known prior art in general.
The present invention utilizes the head of the engine piston or pistons for the formation of a steam generating chamber instead of utilizing the cylinder head for this purpose, as in U.S. Pat. No. 4,301,655. This has several advantages. A much smaller mass of material requiring heating to produce steam is present in the piston head, as compared to the larger cylinder head. It is feasible to employ high temperature materials in the manufacturing of the pistons which can withstand much higher temperatures than the cylinder head, and this factor, together with the smaller mass of the piston, will significantly shorten the time period required for the fuel saving power augmentation cycle to commence during engine operation, compared to the prior art. It is also less costly to provide what amounts to a miniature steam boiler in the head of the piston than to provide the same in the cylinder head.
A further advantage achieved by the improved structure is that the steam generating chamber formed in each piston can serve simultaneously as a pre-combustion chamber of the kind successfully employed in many compression ignition type engines. This achievement of the invention obviates the necessity for a second and separate fuel injection chamber as in U.S. Pat. No. 4,301,655.
As in U.S. Pat. No. 3,959,974, a displacement piston without rings and not requiring lubrication is used and such a piston can withstand extremely high temperatures when fabricated from known high temperature materials, thus enhancing the efficiency of the engine. As a practical matter, a cylinder head cannot be manufactured to withstand such high temperatures.
Other features and advantages of the invention will become apparent during the course of the following description.